Toward catchment hydro-biogeochemical theories

Headwater catchments are the fundamental units that connect the land to the ocean. Hydrological flow and biogeochemical processes are intricately coupled, yet their respective sciences have progressed without much integration. Reaction kinetic theories that prescribe rate dependence on environmental variables (e.g., temperature and water content) have advanced substantially, mostly in well-mixed reactors, columns, and warming experiments without considering the characteristics of hydrological flow at the catchment scale. These theories have shown significant divergence from observations in natural systems. On the other hand, hydrological theories, including transit time theory, have progressed substantially yet have not been incorporated into understanding reactions at the catchment scale. Here we advocate for the development of integrated hydro-biogeochemical theories across gradients of climate, vegetation, and geology conditions. The lack of such theories presents barriers for understanding mechanisms and forecasting the future of the Critical Zone under human- and climate-induced perturbations. Although integration has started and co-located measurements are well under way, tremendous challenges remain. In particular, even in this era of "big data," we are still limited by data and will need to (1) intensify measurements beyond river channels and characterize the vertical connectivity and broadly the shallow and deep subsurface; (2) expand to older water dating beyond the time scales reflected in stable water isotopes; (3) combine the use of reactive solutes, nonreactive tracers, and isotopes; and (4) augment measurements in environments that are undergoing rapid changes. To develop integrated theories, it is essential to (1) engage models at all stages to develop model-informed data collection strategies and to maximize data usage; (2) adopt a "simple but not simplistic," or fit-for-purpose approach to include essential processes in process-based models; (3) blend the use of process-based and data-driven models in the framework of "theory-guided data science." Within the framework of hypothesis testing, model-data fusion can advance integrated theories that mechanistically link catchments' internal structures and external drivers to their functioning. It can not only advance the field of hydro-biogeochemistry, but also enable hind- and fore-casting and serve the society at large. Broadly, future education will need to cultivate thinkers at the intersections of traditional disciplines with hollistic approaches for understanding interacting processes in complex earth systems.This article is categorized under:Science of Water > Method

Interferon β-1a in relapsing multiple sclerosis: four-year extension of the European IFNβ-1a Dose-C omparison Study

Background: Multiple sclerosis (MS) is a chronic disease requiring long-term monitoring of treatment. Objective: To assess the four-year clinical efficacy of intramuscular (IM) IFNb-1a in patients with relapsing MS from the European IFNb-1a Dose-C omparison Study. Methods: Patients who completed 36 months of treatment (Part 1) of the European IFNb-1a Dose-C omparison Study were given the option to continue double-blind treatment with IFNb-1a 30 mcg or 60 mcg IM once weekly (Part 2). Analyses of 48-month data were performed on sustained disability progression, relapses, and neutralizing antibody (NA b) formation. Results: O f 608/802 subjects who completed 36 months of treatment, 493 subjects continued treatment and 446 completed 48 months of treatment and follow-up. IFNb-1a 30 mcg and 60 mcg IM once weekly were equally effective for up to 48 months. There were no significant differences between doses over 48 months on any of the clinical endpoints, including rate of disability progression, cumulative percentage of patients who progressed (48 and 43, respectively), and annual relapse rates; relapses tended to decrease over 48 months. The incidence of patients who were positive for NAbs at any time during the study was low in both treatment groups. Conclusion: C ompared with 60-mcg IM IFNb-1a once weekly, a dose of 30 mcg IM IFNb-1a once weekly maintains the same clinical efficacy over four years

Influence of acid rain on CO2 consumption by rock weathering : local and global scales

Sulphuric and nitric acids, which are supplied by acid precipitation, take over from carbonic acid in weathering reactions, which induced a decrease of the atmospheric/soil CO2 consumption by weathering (WCO2). In order to quantity this disturbance, one has compared the bicarbonate fluxes determined at the outlet of 2 small catchments (one is substantially disturbed and the other is is weakly disturbed by acid precipitation). Out study shows that, under the influence of acid precipitation, bicarbonate fluxes (i.e. WCO2) are decreased by about 73%. It has also been attempted to simulate at the continental scale, the influence of acid precipitation on WCO2, using a Global Erosion Model (GEM-CO2) recently developed. Several simulations have been performed corresponding to different realistic scenarios of global acid precipitation. In the most pessimistic of these scenarios, the GEM-CO2 simulation shows that the global WCO2 would be decreased by no more than 10%

Impact du changement climatique sur l’évolution de la ressource en eau en Bourgogne, France (1980-2100).

6 pagesInternational audienceThe regional climatic model ARW / WRF is used to make a dynamic downscaling of climate (driven by ERA-Interim) at a high spatial resolution (3 km2) over Burgundy, at daily time scale over the period 1980-2011. Climatic simulations were analyzed and compared with meteorological data, in order to validate them with the aim of their use by hydro(geo)logic models. The hydro-climatic parameters necessary as climatic inputs of these models, in particular precipitation and evapotranspiration, reproduce correctly the spatial and temporal variability (in spite of an overestimation of simulated precipitation), which allows their use in a hydro-climatic modelling chain. Keywords: climate change, water resource, regional climate modelling, hydrologic modelling, Burgundy.mation of simulated precipitation), which allows their use in a hydro-climatic modelling chain